Typically semiconductor objects, such as wafers, chips, die, pieces and bars, are stored in storage containers after processing and before implementation into an electronic or computer device. Various types of storage containers exist to protect these semiconductor objects from particulate and handling damage. The problems with the prior art containers occur, however, when attempting to remove the semiconductor objects from the container. Due to the small size and delicate nature of semiconductor objects, electrostatic potential that builds within and around the storage container can cause serious damage to the semiconductor objects upon discharge. There are typically two sources of electrostatic potential: 1) electrostatic transfer from a person or mechanism that removes the semiconductor objects from the storage container and 2) triboelectric discharges that may be present when peeling apart the sheets forming the storage container. Thus, not only are careful storage procedures required, but semiconductor objects must be carefully removed from storage containers.
Semiconductor objects are typically enclosed in a protective envelope to prevent electrostatic discharge damage. The amount of protection a particular protective envelope affords depends greatly on the type of material being used for the envelope. Protective envelopes, however, have presented numerous problems and have been found to be unsatisfactory in reducing the electrostatic discharge damage done to semiconductor objects.
A typical prior art protective envelope is made from a transparent sheet material composed of an electrically non-conductive polymeric sheet. The surface of the envelope is made conductive by applying a special treatment on the polymeric sheet, applying a coating of antistatic material on both surfaces of the polymeric sheet, or disposing antistatic material throughout the polymeric sheet such that the volume conductivity of the polymeric sheet is not significantly increased. The resistivity on the surfaces of the envelope, however, does not permit the envelope to assume the electrostatic potential of a person or mechanism opening the envelope before the semiconductor object is removed. This results in a damaging electrostatic charge being transferred from the person or mechanism to the semiconductor object after the envelope is opened. Since the charges on the person or the mechanism handling the envelope are not rapidly dissipated by the outer surface, they are capacitively coupled through the envelope and cause serious damage to the semiconductor objects therein.
Other types of sheet materials that are used for protective envelopes include high volume conductive carbon loaded polymeric sheets or metal foils. While these protective envelopes are comparatively effective in the dissipation of electrostatic charges, a disadvantage is that they are opaque and do not afford visual identification of the semiconductor objects being stored therein. A further drawback is that contact between the semiconductor object and the inner surface of the envelope causes metal or carbon filled scrapings to contaminate the semiconductor objects. Disadvantageously, such volume conductive sheet materials conduct electrostatic charges directly to the semiconductor object within the envelope. That is, the inner surface of the plastic bag does not dissipate the charges on the semiconductor object caused during processing and storage and the triboelectric charges caused by the relative movement between the objects and the inner surface of the polymeric bag.
Another method of minimizing ESD damage is to flood the work area surrounding the object with ionized air while removing the semiconductor object from the storage container. Although the risk of electrostatic charge transfer between the person or mechanism removing the semiconductor objects may be reduced, this method is ineffective in dissipating the triboelectric charge generated between the insulating surfaces, where the semiconductor objects are stored, when the surfaces are peeled apart.